In a monitoring system or the like, there is known a technique for detecting an object included in an image and automatically tracking the movement of the object. The tracking of the object can be implemented by, e.g., acquiring a difference between an image that does not include a target object to be tracked and an image that includes the target object to be tracked to generate a template, and searching the image frame by frame by using the template (PTL 1).
As a system to which the tracking of the object is applied, a traffic flow measurement system is known. It is possible to count the number of vehicles having passed a target point by shooting a video of a road by using, e.g., a camera installed on the roadside and tracking passing vehicles (PTL 2).